JPH04339302A - Beat canceller circuit for tape recorder - Google Patents

Abstract

PURPOSE:To always perform sound recording in best condition while using a bias oscillation frequency as a basic frequency regardless of the position of a beat canceller switch at the time of recording FM broadcasting in which a beat does not cause a problem. CONSTITUTION:At the time of recording AM broadcasting, a control terminal 6a of a system control circuit 6 outputs a voltage signal at an H level to validate the switchover of the frequency by a beat canceller switch 16, and at the time of the occurrence of the beat, by operating the beat canceller switch to connect an auxiliary resonance capacitor 15 in parallel with a main resonance capacitor 13 and switching over the bias oscillation frequency, the occurrence of the beat is reduced. At the time of recording the FM broadcasting, by making the control terminal 6a output the voltage signal of an L level to invalidate a switching circuit 14 regardless of the position of the beat canceller switch, the auxiliary resonance capacitor is disconnected from the main resonance capacitor and the bias oscillation frequency is used as the reference frequency.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beat canceller circuit for a tape recorder that can select and record signals received by a tuner and other desired signals.

0002

[Prior Art] Conventionally, in a tape recorder with a radio, for example, which can record signals received by a tuner section, when a beat sound occurs between the bias oscillation frequency and the reception frequency, the bias oscillation frequency is changed to prevent this. A beat canceller switch is provided for manual switching.

[0003] Although this beat canceller switch is actually switched when recording AM broadcasts such as LW band and MW band, which have low receiving frequencies where beat sounds are likely to occur, it is also used when recording FM broadcasts and radio signals that are less likely to produce beat sounds. If you record a source other than 1, it will not be switched.

[0004] For this reason, once the beat canceller switch is switched to eliminate the beat sound during AM broadcast recording such as the LW band or MW band, it is left as it is and remains in the switched position even after AM recording is finished. Most of the time. Originally, when trying to make good recordings with a tape recorder, when the signal has a narrow band such as AM broadcasting and the S/N ratio is not very good, even if the bias oscillation frequency is changed by the beat canceller switch, Although it is not a big problem, sources other than FM broadcasts and radio, such as CDs,
When receiving a high-quality signal with a wide band and a large dynamic range, such as a compact disc, it is desirable that the beat canceller switch be switched to the reference bias frequency. This is because the tape recorder's bias oscillation circuit and other recording circuits are designed and adjusted so that the best recording characteristics are obtained when the beat canceller switch is at the reference frequency position.

[0005]

[Problems to be Solved by the Invention] However, in the conventional configuration, as mentioned above, the beat canceller switch is switched to a side different from the reference frequency in order to prevent the generation of beat sound when recording AM broadcasts such as LW band and MW band. Even if the beat canceller switch is located on the back of the device's cabinet, it is easy to record other sources without knowing it. For this reason, there has been a problem in that the recording operation is not necessarily performed in the best condition.

[0006] The present invention was made in order to improve these points, and it is possible to always record a source in which the beat is not a problem in the best condition regardless of the position of the beat canceller switch. The present invention provides a beat canceller circuit devised to achieve this.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a tape recorder that selects and records signals received by a tuner and signals input from other sources, and a recording magnetic head that is used during recording. a bias oscillation circuit that supplies a bias to the bias oscillation circuit; and a switching circuit that includes a beat canceller switch and switches the oscillation frequency of the bias oscillation circuit in accordance with the operation of the switch;
a control circuit that controls the switching circuit according to the reception band of the tuner and the input source to enable or disable the frequency switching of the beat canceller switch; The oscillation frequency of the bias oscillation circuit is set to a reference frequency.

[0008]

[Operation] With the above configuration, when recording AM broadcasts such as LW band and MW band, by enabling the frequency switching of the beat canceller switch, the oscillation frequency of the bias oscillation circuit is switched by operating the beat canceller switch and the beat canceller switch is enabled. On the other hand, when recording sources other than FM broadcasts or radio reception, the beat canceller switch is disabled and the bias oscillation circuit is turned off regardless of the position of the switch. By setting the oscillation frequency to the reference frequency, recording can be achieved in the best possible condition. Therefore, there is no need to check the position of the beat canceller switch every time when recording an FM broadcast, etc., and there is no possibility of recording in an unfavorable state due to forgetting to check the position.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, a tape recorder with a radio equipped with a PLL frequency synthesizer type electronic tuner will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing the circuit configuration in this embodiment. Reference numeral 1 denotes a synthesizer-type electronic tuner section, which includes a radio broadcast receiving and demodulating section. 2
3 is a band selection switch section for selecting the radio broadcasting band desired by the user, and 3 is an electronic tuner section 1.
A tuner control circuit (for example, a microcomputer) that controls the display unit 4, etc. that displays the reception band, reception frequency, etc.
Various control signals are output from the control terminal 3a.

Reference numeral 5 denotes a source changeover switch unit for selecting a desired source; 6, the source changeover switch unit 5, an indicator unit 7 for displaying the selected source, etc., of the radio-equipped tape recorder; A system control circuit (e.g., a microcomputer) that comprehensively controls the entire operation, and a control signal from the control terminal 6a of the tuner control circuit 3 according to the control signal from the control terminal 3a and the source selected by the source changeover switch section 5. Outputs a control signal.

8 is a head section consisting of magnetic heads 9 and 10 for recording and reproducing left and right channels and a magnetic head 11 for erasing;
Reference numeral 12 indicates a bias oscillation circuit that supplies bias to the head section 8, and reference numeral 13 indicates a main resonance capacitor for determining the oscillation frequency of the bias oscillation circuit 12.

14 is a switching circuit that switches the oscillation frequency of the bias oscillation circuit 12 by connecting or disconnecting the auxiliary resonant capacitor 15 in parallel to the main resonant capacitor 13;
Contains 6. This beat canceller switch switch 1
Reference numeral 6 controls switching of the switching circuit 14 in accordance with the switching operation, and connects or disconnects the auxiliary resonant capacitor 15 in parallel to the main resonant capacitor 13. The oscillation frequency of the bias oscillation circuit 12 is set to be the reference frequency when the auxiliary resonant capacitor 15 is not connected in parallel to the main resonant capacitor 13. The switching circuit 14 is also controlled by two types of control signals from the control terminal 6a of the system control circuit 6, and the frequency switching by the beat canceller switch 16 is enabled or disabled by these two types of control signals.

Next, the operation of the above configuration will be explained below. First, as a first case, a case will be described in which an AM broadcast radio signal in the LW band or MW band, in which beat generation is a problem during recording, is received and recorded by a tape recorder section.

When, for example, the MW band is selected in the band changeover switch section 2, the tuner control 3 determines whether or not the frequency change by the beat canceller switch 16 should be enabled based on the signal from the band changeover switch section 2. As a result of the determination, a control signal for validating the frequency switching is outputted from the control terminal 3a to the system control circuit 6. When the system control circuit 6 receives the control signal, it outputs from the control terminal 6a a control signal (H level voltage signal) to enable frequency switching by the beat canceller switch 16, and inputs it to the switching circuit 14. ,
Frequency switching by the beat canceller switch 16 is enabled.

In the illustrated state, the beat canceller switch 16 is on the reference frequency side, and the switching circuit 14
is in an off state, and the auxiliary resonant capacitor 15 is electrically disconnected from the main resonant capacitor 13,
The oscillation frequency of the bias oscillation circuit 12 is a reference frequency.

If a beat occurs in such a state, if the user operates the beat canceller switch 16 to the side that reduces the beat (upward in the drawing), the switching circuit 14 is turned on and the auxiliary resonance capacitor is switched on. 15 is connected in parallel to the main resonant capacitor 13, and the oscillation frequency of the bias oscillation circuit 12 is switched from the reference frequency to a predetermined frequency. As a result, good AM broadcast recording without beats can be performed.

Next, as a second case, FM band etc.
A case will be explained in which a radio signal with negligible beats during recording is received and recorded on the tape recorder section.

When, for example, the FM band is selected in the band changeover switch section 2, the tuner control circuit 3 determines whether or not the frequency change by the beat canceller switch 16 should be enabled based on the signal from the band changeover switch section 2. As a result of the determination, a control signal for disabling the frequency switching is outputted from the control terminal 3a to the system control circuit 6. Then, the system control circuit 6 receives the control signal and outputs a control signal (an L-level voltage signal) to the switching circuit 14 from the control terminal 6a to disable the frequency switching by the beat canceller switch 16.

Therefore, even if the beat canceller switch 16 were to be switched to a side different from the reference frequency side, the switching circuit 14 would not be turned on but would remain in the off state, and the auxiliary resonant capacitor 15 would be It is in a state where it is disconnected from the main resonant capacitor 13. As a result, the oscillation frequency of the bias oscillation circuit 12 is the reference frequency, and it is possible to record the FM radio signal in the best condition. Finally, the case where a source other than a radio signal is recorded by the tape recorder section will be explained.

When the source selection switch section 5 is operated and a signal from the switch section 5 is input to the system control circuit 6, the control circuit 6 switches the beat canceller switch 16 regardless of the input signal from the tuner control circuit 3. A control signal for disabling frequency switching by the control terminal 6a is output from the control terminal 6a. Then,
The oscillation frequency of the bias oscillation circuit 12 is at the reference frequency for the same reason as in the second case, so that recording of sources other than radio signals can be performed in the best condition.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can of course be practiced with appropriate modifications within the scope of the gist.

[0023]

As described above, according to the present invention, it is possible to prevent the generation of beat sound when recording radio broadcasts in the LW band or MW band by operating the beat canceller switch, and also to prevent the generation of beat sounds during FM broadcasts in which beat sounds are less likely to occur. When recording sources other than FM or radio signals, you can always record in the best condition by using the bias oscillation frequency as the reference frequency regardless of the position of the beat canceller switch. There is no need to check the position one by one, and there is no need to record in an unfavorable state due to forgetting to check, which is excellent in practical use.

[Brief explanation of drawings]

[Fig. 1] Circuit configuration diagram showing one embodiment of the present invention

[Figure 2] Diagram showing a specific example of the switching circuit

[Explanation of symbols]

1 Electronic tuner section 3 Tuner control circuit 6 System control circuit 8 Head part 12 Bias oscillation circuit 13 Main resonance capacitor 14 Switching circuit 15 Auxiliary resonant capacitor 16 Beat canceller switch

Claims (1)

[Claims] Claim 1: A tape recorder that selects and records signals received by a tuner and signals input from other sources, including a bias oscillation circuit that supplies a bias to a recording magnetic head during recording, and a beat canceller switch. , a switching circuit that switches the oscillation frequency of the bias oscillation circuit in accordance with the operation of the switch;
a control circuit that controls the switching circuit according to the tuner's reception band and input source to enable or disable frequency switching by the beat canceller switch; A beat canceller circuit for a tape recorder, characterized in that the oscillation frequency of the bias oscillation circuit is set to a reference frequency.